EXPRESSION OF GIFSY-1 PROPHAGE SMALL RNA INTERFERES WITH BACTERIAL TRANSCRIPTION TERMINATION

Shoshy Altuvia ¹ Tal Hershko ¹ Ahuva Odenheimer ¹ Maya Elgrably-Weiss ¹ Tamar Ben-Zvi ¹ Hemda Seri ¹ Kai Papenfort ² Jörg Vogel ²

¹Microbiology and Molecular Genetics, The Hebrew University of Jerusalem-Hadassah Medical School, Jerusalem, Israel
²Institute for Molecular Infection Biology, University of Würzburg, Würzburg, Germany

While an increasing number of conserved small regulatory RNAs (sRNAs) are known to function in general bacterial physiology, the roles and modes of action of sRNAs from horizontally acquired genomic regions remain little understood. IsrK sRNA of Gifsy-1 prophage of Salmonella belongs to the latter class. This regulatory RNA exists in two isoforms. The first forms, when a subset of transcripts originating from isrK promoter, read-through IsrK transcription-terminator producing translationally inactive target mRNA. Acting in trans, short IsrK RNA, the second isoform, binds the inactive transcript rendering it translationally active. By switching on translation of the first isoform, short IsrK leads to the production of an antiterminator protein that interferes with bacterial transcription termination causing growth arrest and ultimately cell death. To our knowledge this study describes a unique example of an island-encoded sRNA that exerts a highly complex regulatory cis and trans mechanism aimed at silencing or inducing toxic proteins.